Benjamin Still

Monitoring the Soil Freeze-Thaw Process Using Piezoceramic-Based Smart Aggregate

AbstractMonitoring the soil freeze-thaw process is of great importance to engineering design of infrastructure, observation of hydrology, variation of climate, and existence of vegetation in cold regions. This paper presents experimental results to describe the soil freeze-thaw process using piezoceramic-based smart aggregate (SA) transducers. Two SAs are embedded in predetermined locations: one is used as the actuator and the other is used as a sensor. The active-sensing method is applied to excite a stress wave propagating between the two SAs. The alteration of the mechanical properties of the soil during the freeze-thaw process has an important effect on the stress-wave propagation, and the transition between the freeze and thaw states of the soil is monitored in real time. A wavelet packet-based soil freeze-thaw status indicator is established to quantitatively describe the soil status during the freeze-thaw process. Potentially, this freeze-thaw status indicator can be linked to soil mechanical prope...

Physical and Mechanical Properties of Fungal Mycelium-Based Biofoam

AbstractThis paper presents an innovative fungal mycelium-based biofoam. Three different mixing protocols with various substrate materials, including wood pulp, millet grain, wheat bran, a natural ...

Shear properties of thawed natural permafrost by bender elements

Thawed permafrost could cause a serious stability problem for foundations and oil-wells in cold regions. A non-damage testing procedure, employing the Bender Element Method, was used for permafrost samples collected from a continuous frozen core obtained from the North Slope of Alaska, USA. The wave velocity and modulus of thawed permafrost were investigated on various isotropic confining pressure from 0 kPa to 400 kPa per 100 kPa. The received shear wave propagation was recorded, and the elastic wave theory was used to calculate shear modulus. Finally, the shear modulus affected by confining pressure, water content and dry density were analyzed and discussed, and a regression formulation of shear modulus based on the Janbu Model for thawed silty and sandy permafrost were proposed and validation.

Mechanical Properties of Naturally Frozen Silty Soil for Seismic Design of Pile Foundations

Frozen soils, especially seasonally frozen soils, have great impact on the seismic performance of bridge pile foundations. To account for its impact on pile foundations in the seismic analysis of bridge foundations, it is necessary to evaluate the mechanical properties of naturally frozen soil samples at a strain rate that is compatible to that induced in the frozen soil during a seismic event. This paper presents the mechanical properties obtained from testing of naturally frozen silty soils in Alaska. Uniaxial compression tests were conducted on naturally frozen soils including both seasonally frozen soils and permafrost obtained from Alaska. All tests were conducted at a constant deformation rate corresponding to a strain rate of 0.1%/s. Both horizontal and vertical specimens are tested under various temperatures below the freezing point. Testing results including soil characteristics and mechanical properties such as stress-strain curves, compressive strength, modulus of elasticity, and strains corresponding to the peak compressive strength and 50% of peak strength are presented. The impact of temperature and dry density on the mechanical properties is discussed.